Welcome to the forum!
There's a Land Rover show at the Three Counties Showground in Malvern on the 18th and 19th of May. There will be lots of parts for sale plus other Landies to look at. Of course that can often be an annoying and costly pastime as you often see bits you didn't know existed and then want them for your own Landy.
As for your radio, if it's a standard Land Rover one, i would have thought your local dealer would be able to help if you take along your V5 to prove you're the owner.